Effect of fluorescein‐family and other dyes on the growth of the red tide organism Ptychodiscus brevis

Abstract

Abstract Fluorescein family dyes (substituted xanthenylbenzoates: fluorescein, erythrosin, eosin Y, and rose bengal) were used to evaluate the effect of known singlet‐oxygen sensitizers on the unarmored dinoflagellate Ptychodiscus brevis. Cells were enumerated after 24 hours in the presence of 1 x 10−4 M dye solution. Results were also compared using cells in the presence and absence of light and for both conditions in the presence and absence of dyes. The effect was expressed as percent cells surviving, and the order of effectiveness was: fluorescein < eosin Y < erythrosin < rose bengal. Methylene blue and ZPS were also used to be certain that the effect was not simply a structural effect of substituted fluoresceins. Percent survival was a linear function of the known quantum yield of the sensitizers (r = ‐0.937 ; P = 0.03). Ptychodiscus brevis is known to be unique among dinoflagellates for the lack of peridinin, a fairly common pigment that serves as a singlet oxygen quencher. The implications of these...